DE112013006240T5 - Multi-layer thin film for cutting tool and cutting tool with it - Google Patents

Abstract

There is provided a multi-layer thin film for a cutting tool in which micro-scale thin films ranging in thickness from a few nanometers to tenths of nanometers are stacked alternately, which has less quality differences and is capable of realizing excellent wear resistance. The multilayer thin film according to the present disclosure is a multilayer thin film for a cutting tool in which thin film units each consisting of the thin films A, B, C, and D are stacked more than once, wherein the moduli of elasticity of the thin films are KA > kB, kD> kC or kC> kB, kD> kA, the lattice parameters L of the thin films satisfy the ratios LA, LC> LB, LD or LB, LD> LA, LC, and a difference between the maximum values and the minimum ones Values of the lattice parameter L is 20% or less.

Description

Technical area

The present disclosure relates to a multi-layer thin film for a cutting tool, and more particularly to a multi-layer thin film for a cutting tool in which a superlattice thin film having a thickness of a few nanometers to tenths of nanometers is stacked in the form of ABCD or ABCB having less quality differences and is able to realize excellent wear resistance.

State of the art

Since the late 1980s, various TiN-based multi-layer film systems have been proposed to develop materials for a cutting tool with a high hardness.

For example, a multilayer film formed by alternately and repeatedly stacking TiN or VN to a thickness of a few nanometers forms a so-called superlattice having a single lattice parameter and coherent intersectional areas instead of differences in the lattice parameters of the individual layers. With this coating, twice as high or even greater hardness compared to the general hardness of each individual layer can be achieved, so that there have been numerous attempts to use this phenomenon for the coating of cutting tools.

Examples of reinforcement mechanisms used for these superlattice coatings include Koehler's model, the Hall-Petch relationship, and a coherence-strain model, and these reinforcement mechanisms refer to a hardness increase by a difference between the lattice parameters of A and B, a Difference between the moduli of elasticity of A and B and the control of the stacking periods of A and B with an alternating application of materials A and B.

Basically, it is difficult to apply two or more reinforcing mechanisms by alternately stacking two materials. In particular, the production of a multi-layer thin film having excellent wear characteristics and consistent quality under the conditions of mass production poses difficulties in which large deviations in a stacking period of the multi-layer thin film exist both between the various batches and within a batch.

As in 1 Therefore, in producing a multilayer thin film by alternately stacking two or more materials, it has conventionally been conventional to perform stacking so that an elastic period and a grating period coincide, as in FIG U.S. Patent No. 5,700,551 described. However, in this case, it is difficult to apply the aforementioned various reinforcing mechanisms, so that the improvement of the wear resistance of the multilayered film is limited here.

Disclosure of the invention

Technical task

The object of the present disclosure is to provide a multilayer thin film for a cutting tool having superior wear resistance over conventional superlattice coatings during manufacture of the multilayer thin film from a superlattice, and a multi-layer thin film coated cutting tool, adjusting a grating period and an elastic period of the multilayer thin film so that two or more thin film reinforcing mechanisms act on the multilayer thin film.

Technical solution

In order to achieve the above technical object, the present disclosure provides a multilayer thin film for a cutting tool in which thin film units each consisting of the thin films A, B, C, and D are stacked more than once, the elastic moduli k of the thin films, the ratios k _{A> B} k, k satisfy _D> k _A, the lattice parameter L k _D> k _C or _C k> k _B, of the thin films satisfy the ratios L _A , L _C > L _B , L _D or L _B , L _D > L _A , L _C , and a difference between the maximum values and the minimum values of the lattice parameters L is 20% or less.

In the multilayer thin film according to the present disclosure, an average grating period l _{L of} the multilayer thin film may be one half of an average elastic period l _k thereof.

In the multilayer thin film according to the present disclosure, the thin film unit may have a thickness of 4 to 50 nm, and preferably 10 to 30 nm.

In the multilayer thin film according to the present disclosure, the thin films B and D may be made of the same material.

In addition, the present disclosure provides a cutting tool whose surface is coated with the multilayer thin film.

Advantageous effects

According to the present disclosure, in forming a multilayer superlattice thin film of such a type that four or more thin film units are laminated into a film and the laminated film is then repeatedly stacked into two or more layers, changes in stacking periods of the elastic moduli and the lattice parameters corresponding to the stacking period can be made of the thin film unit, as in 2 so that two or more reinforcing mechanisms act on the multilayer thin film. As a result, a multi-layer thin film for a cutting tool can be provided which has less quality variations and better wear resistance compared to a multilayer thin film on which only a single reinforcing mechanism acts.

Brief description of the drawings

1 Fig. 14 shows the relationship between an elastic period and a grating period in a conventional multilayer superlattice thin film.

2 Fig. 14 shows the relationship between an elastic period and a grating period in a multilayer superlattice thin film according to the present disclosure.

3 Fig. 12 is a graph showing the changes in a lattice parameter corresponding to the aluminum content in a (Ti _1-x Al _x ) N-based thin film.

4 Fig. 14 shows photographs of the test results of the cutting performance of a multilayer thin film according to Example 1 of the present disclosure and a multilayer thin film according to a comparative example.

5 Fig. 12 shows photographs of the test results of the cutting performance of a multilayer thin film according to Example 2 of the present disclosure and a multilayer thin film according to a comparative example.

Embodiment mode of the invention

Hereinafter, the present disclosure will be described in detail based on preferred embodiments, and the inventive idea is not limited to the embodiments below.

The inventors of the present invention found that, when an elastic period and a grating period when stacking a thin film unit behave differently from each other instead of coinciding, two or more amplification mechanisms (ie, the mechanism of the Koehler's model and the mechanism of the Hall-Petch). Relationship), particularly in a laminated superlattice film, whereby the wear resistance of the multilayer film is improved, while at the same time reducing quality variations in mass production over a multilayer film in which mainly a single reinforcing mechanism acts, thus completing the present invention.

The multilayer thin film according to the present disclosure is a multilayer thin film for a cutting tool in which a thin film formed by sequentially stacking thin film units each consisting of the thin films A, B, C, and D repeats into two or more layers stacked on top of each other, wherein the moduli of elasticity k of the thin-film units satisfy the ratios k _A > k _B , k _D > k _C or k _C > k _B , k _D > k _A , the lattice parameters L of the thin-film units are L _A , L _C > L _B , L _D or L _B , L _D > L _A , L _C , and a difference between the maximum values and the minimum values of the lattice parameters L is 20% or less.

2 FIG. 16 shows an example of the relationship between an elastic period and a grating period in a multilayer superlattice thin film according to the present disclosure. FIG. As in 2 4, it can be seen that the multi-layered superlattice thin film differs in that from FIG 1 distinguishes that the elastic period (blue) is about twice as large as the grating period (red) and thus the elastic period and the grating period do not coincide.

In the Koehler elastic modulus model, it is described that the reinforcing effect arises when the thickness of the thin films A and B becomes so small as to become less than or equal to 20 to 30 nm, corresponding to a thickness of about 100 atomic layers is a critical thickness at which it is difficult to produce a dislocation. The inventive idea is that the elastic period and the lattice parameter period are adjusted in disagreement with each other so that the two amplification effects can be generated.

Further, it is difficult to form the superlattice when the difference between the maximum values and the minimum values of the lattice parameter L is larger than 20%. Therefore, the grating parameter is preferably adjusted so that the difference is in the range of 20%, or less if possible.

In the multilayer thin film according to the present disclosure, it is provided that the thin film units consist of four layers, and the stacking of each thin film unit is performed in the order of A-B-C-D or A-B-C-B. That is, the second and fourth layers may be formed of different materials or the same material.

Further, a difference between an average elastic period and an average lattice parameter period falls within the scope of the present disclosure, and preferably, the average elastic period is twice as wide as the average lattice period.

[Example]

Before forming a multilayer superlattice thin film in which a thin film of four thin film units is repeatedly stacked into two or more layers, a single-layer thin film was applied to measure the Young's modulus of each thin film unit and to confirm the Young's modulus of each thin film unit. The results are shown in Table 1.

For applying the thin film unit, arc ion plating was used, which is a vacuum evaporation method (PVD). The initial vacuum pressure was lowered to 8.5 × 10 ^-5 Torr or less, then N _{2 was introduced} as a reaction gas, and the coating was carried out under the condition of a reaction gas pressure of 40 mTorr or less (preferably 10 to 35 mTorr), a temperature of 400 to 600 ° C and a substrate bias of -30 to -150 V. Table 1 thin Target composition (in%) Young's modulus k (GPa) TiN Ti = 99.9 416 TiAlN Ti: Al = 75:25 422 TiAlN Ti: Al = 50:50 430 AlTiN Ti: Al = 33:67 398 CrN Cr = 99.9 475 CrAlN Cr: Al = 50:50 367 AlCrNN Cr: Al = 30:70 403 AlCrSiN Cr: Al: Si = 30: 65: 5 338

The lattice parameters of the individual thin film units forming the multilayer thin film can be determined by using X-ray diffraction analysis after forming the single-layer thin film, but the lattice parameters of the individual thin film units in the embodiment of the present disclosure were determined using atomic radius, ion radius and covalent radius came from existing experiments and theories. Specifically, the lattice parameter was calculated by quantitatively applying the covalent radius to a B1 HCP structure in accordance with the atomic ratio.

As in 3 In the case of the (Ti _1-x Al _x ) N-based thin film, the lattice parameter tends to decrease approximately linearly with increasing aluminum content, so that the lattice parameter of the (Ti _1-x Al _x ) N-based thin film is represented by Equation 1 can be obtained below.

[Equation 1]

• Lattice parameters: a = 4.24 Å - 0.125 x Å (x is a molar ratio of aluminum)

example 1

In Example 1 of the present disclosure, the production of a TiAlN-based multilayer thin film according to the method of the present disclosure was compared with the production of a TiAlN-based multilayer thin film according to a conventional method.

The stack structures and multilayer thin film compositions were determined as shown in Table 2 below. A thin film consisting of four thin film units was stacked a total of 180 times so that an average grating period was 5 to 10 nm and the elastic period was 10 to 20 nm, and thus a multilayer film having a final film thickness of 2.6 to 3 , 2 μm was obtained. In this case, A30 (Model No. SPKN1504EDSR), which is a P30 material available from Korloy, was used as a substrate to which the multilayer thin film was applied. Table 2 thin aim A B C D annotation 1-1 composition Ti: Al = 50:50 Ti: Al = 75:25 Ti: Al = 33:67 Ti: Al = 75:25 example lattice parameters 423 442.5 409.7 442.5 modulus of elasticity 430 422 398 422 1-2 composition Ti: Al = 33:67 Ti: Al = 33:67 Ti: Al = 75:25 Ti: Al = 75:25 Comparative example lattice parameters 409.7 409.7 442.5 442.5 modulus of elasticity 398 398 422 422 1-3 composition Ti: Al = 33:67 Ti: Al = 75:25 Ti: Al = 33:67 Ti: Al = 75:25 Comparative example lattice parameters 409.7 442.5 409.7 442.5 modulus of elasticity 398 422 398 422 1-4 composition Ti: Al = 33:67 Ti: Al = 33:67 Ti: Al = 50:50 Ti: Al = 50:50 Comparative example lattice parameters 409.7 409.7 423 423 modulus of elasticity 398 398 430 430 1-5 composition Ti: Al = 33:67 Ti: Al = 50:50 Ti: Al = 33:67 Ti: Al = 50:50 Comparative example lattice parameters 409.7 423 409.7 423 modulus of elasticity 398 430 398 430

In Table 2, the unit of the lattice parameter is Å and the unit of elastic modulus is GPa.

SKD11 (width: 100 mm, length: 300 mm) was used as a workpiece for the evaluation of the cutting performance of the multilayer thin film applied above, and the cutting was carried out under dry conditions at a cutting speed of 250 m / min, a feed per tooth of 0.2 mm / tooth and a feed of 2 mm. The cutting performance was evaluated by comparing the wear after chipping of 900 mm. The results are in 4 listed.

As in 4 As shown, wear during chipping of the SKD11 mainly develops as a scoring wear, and it can be confirmed that the scoring characteristics in Example 1-1 are improved as compared with Comparative Examples 1-2 to 1-5.

Example 2

In Example 2 of the present disclosure, the production of an AlCr-based multi-layer thin film according to the method of the present disclosure was compared with the production of an AlCr-based multi-layer thin film by a conventional method.

The stack structures and compositions of the multilayer thin film were determined as shown in Table 3 below. A thin film consisting of four thin film units was stacked a total of 180 times so that an average grating period was 5 to 10 nm and the elastic period was 10 to 20 nm, and thus a multilayer film having a final film thickness of 2.3 to 2 , 6 μm was obtained. In this case, a K44UF material (Model No. BE2060) available from KFC Co. was used as a substrate to which the multilayer thin film was applied. Table 3 thin viewing unit A B C D annotation 2-1 composition Cr: Al: Si = 30: 65: 5 Cr: Al = 50:50 Cr: Al = 30:70 Cr: Al = 50:50 example lattice parameters 393.8 402 382.7 402 modulus of elasticity 338 367 403 367 2-2 composition Cr = 99.9 Cr: Al = 30:70 Cr: Al = 50:50 Cr: Al = 30:70 example lattice parameters 420 382.7 402 382.7 modulus of elasticity 475 403 367 403 2-3 composition Cr: Al = 30:70 Cr: Al = 50:50 Cr: Al = 30:70 Cr: Al = 50:50 Comparative example lattice parameters 382.7 402 382.7 402 modulus of elasticity 403 367 403 367

In Table 3, the unit of the lattice parameter is Å and the unit of elastic modulus is GPa.

For the evaluation of the cutting performance of the multilayer thin film applied above, SM45C (width: 90 mm, length: 300 mm) was used as a workpiece, and the cutting was performed under dry conditions at a cutting speed of 250 m / min., A feed per tooth of 0.2 mm / tooth and a feed of 2 mm. The wear was compared after the cutting of 12,000 millimeters. The results are in 5 to see.

As in 5 As can be seen, Examples 2-1 and 2-2 of the present disclosure show better scoring wear characteristics and flank wear characteristics than Comparative Example 2-3.

That is, a multilayer superlattice thin film stacked such that the elastic period and the grating period are controlled according to the present disclosure has better wear properties over other cases.

Claims (5)

Multilayer thin film for a cutting tool in which thin film units each formed of thin films A, B, C and D are stacked more than once, wherein the moduli of elasticity k of the films are k _A > k _B , k _D > k _C or k _C> k _B satisfying k _D> k _a, the lattice parameter L of the thin films meet the conditions L _a, L _C> L _B, L _D or L _B, L _D> L _a, L _C, and a difference between the maximum and minimum values of the lattice parameter L is 20% or less. The multi-layer thin film according to claim 1, wherein an average lattice parameter period ℓ _{L of} the multilayer thin film is half of an average Young's modulus period ℓ _k thereof. The multi-layer thin film according to claim 1 or 2, wherein the thin film unit has a thickness of 4 to 50 nm. The multi-layer thin film according to claim 1 or 2, wherein the thin films B and D are made of the same material. A cutting tool coated with the multilayer thin film according to claim 1 or 2.

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